A primary, respectively main flow directed through a flow channel is deflected by a lateral pressure gradient parallel to the bounding wall. Since, due to the lower velocity thereof, flow layers proximal to the wall are deflected to a greater degree than flow layers distal to the wall, a secondary flow, respectively a channel vortex forms that is superimposed on the main flow, thereby leading, inter alia, to pressure losses. Such secondary flows regularly occur in blade cascades of turbomachines, such as gas and steam turbines. The blade cascades are composed of a plurality of circumferentially side-by-side disposed blades, respectively blades that are configured in an axially symmetrical flow channel and between each of which a blade channel is formed. The blade channels are radially bounded by a radially, outer housing-side side wall and by a radially inner, hub-side side wall. The sides walls are constituted, for example, of a stationary housing section, rotor sections, radially inner blade platforms and/or radially outer blade cover plates. The blade channels are each circumferentially bounded by a pressure-side and a suction-side blade wall. To reduce the secondary flows, contours in the form of elevations and/or depressions are frequently introduced into the side walls. The European Patent Application EP 2 261 462 A1 and the International Patent Application WO 98/44240 A1 describe examples of such, in particular circumferentially asymmetrical side-wall contours.